Chap. V. 



OSTEOLOGICAL DIFFERENCES. 



173 



the skull is more globular : all the bones of the face are much 

 shortened, and the front of the skull and descending nasal bones are 

 almost perpendicular : the maxillo-jugal arch and premaxillary 

 bones form an almost straight line ; the space between the pro- 

 minent edges of the eye-orbits is depressed. In the Barb the pre- 

 maxillary bones are much shortened, and their anterior portion is 

 thicker than in the rock-pigeon, as is the lower part of the nasal 

 bone. In two Nuns the ascending branches of the premaxillaries, 

 near their tips, were somewhat attenuated, and in these birds, as 

 well as in some others, for instance in the Spot, the occipital crest 

 over the foramen was considerably more prominent than in the 

 rock-pigeon. 



In the lower jaw, the articular surface is proportionably smaller 

 in many breeds than in the rock-pigeon ; and the vertical diameter, 



Fig. 25. — Lower jaws, seen from above, of natural size. A. Rock-pigeon. B. Runt. 



C. Barb. 



more especially of the outer part of the articular surface, is con- 

 siderably shorter. May not this be accounted for by the lessened 

 use of the jaws, owing to nutritious food having been given during 

 a long period to all highly improved pigeons ? In Eunts, Carriers, 

 and Barbs (and in a lesser degree in several breeds), the whole side 

 of the jaw near the articular end is bent inwards in a highly re- 

 markable manner ; and the superior margin of the ramus, beyond 

 the middle, is reflexed in an equally remarkable manner, as may be 

 seen in the accompanying figures, in comparison with the jaw of 

 the rock-pigeon. This reflection of the upper margin of the lower 

 jaw is plainly connected with the singularly wide gape of the 

 mouth, as has been described in Runts, Carriers, and Barbs. The 

 reflection is well shown in fig. 26 of the head of a Runt seen from 

 above; here a wide open space may be observed on each side, 

 between the edges of the lower jaw and of the premaxillary bones. 



